Associated colloids or micelles are the substances when dissolved in a medium behave as normal electrolytes at low concentration but behave as colloids at higher concentration due to the formation of aggregated particles. These aggregates thus formed are called micelles. They are capable of forming ions. The common examples of micelles are soaps and detergents. Micelles may contain as many as 100 molecules or more.

Peptization is the process which involves the conversion of freshly prepared precipitate into a colloidal solution by adding any suitable electrolyte. The electrolyte added into the precipitate is called peptizing agent or the dispersion agent. For example, if freshly prepared ferric hydroxide is treated with the small quantity of FeCl 3 (electrolyte) solution, a dark reddish brown colloidal solution Fe ( OH ) 3 is obtained. Here ferric chloride ( FeCl 3 ) is a peptizing agent.

Desorption is the reverse process of adsorption where the removal of adsorbate from the surface of the adsorbent takes place. This phenomenon is very common in gases that are adsorbed on the surface of fine metals. This process can be brought by heating. That heat energy that absorbed helps in weakening the force that binding both adsorbent and adsorbate. Hence, it is the endothermic process.

What is Brownian movement ?

The Brownian movement in a colloidal system is caused by the unequal bombardment of the molecules of the dispersion medium on the colloidal particles. When more molecules strike the particles on one side, the direction of the motion of particles changes. This is only visible through ultramicroscope. In colloidal solutions, the colloidal particles are in constant zig-zag motion known as Brownian motion. This phenomenon was first observed by Sir Robert Brown in the year 1827.